The stretch reflex, also called the myotatic reflex, is a protective response to stretching. The body protects the stretched muscle by forcefully contracting it. Certain types of physical training take advantage of the stretch reflex to create more power. Use the biceps stretch reflex to perform the pullup exercise.
Stretch Reflex
Muscles contain receptors, called muscle spindles, that detect changes of length within the muscle fibers. When you stretch your bicep, or any muscle, the spindles send a signal to the brain to measure and adjust the stretch, if needed. If the brain deems the stretch too intense or forceful, it activates the stretch reflex, which causes the muscle to suddenly contract. This protects the muscle from an excessive stretch and possible tissue damage.
Biceps Stretch Reflex
When the doctor taps your knee, causing your lower leg to kick out, she is testing your stretch reflex. The tap activates the tendons below your kneecap. It suddenly stretches the tendons and their muscle spindles, causing the body to initiate the stretch reflex. Your quadriceps contract and cause your lower leg to jerk. The tendons of the biceps muscles that activate the stretch reflex are on the inner side of your forearm at the elbow bend. Tapping these tendons result in the biceps contracting, causing your forearm to jerk.
Plyometric Training
Plyometric training involves jumping, hopping or pushing against something forcefully to propel the body in the opposite direction, such as a clap pushup. The stretch reflex is one of the components that provide the body with the power and energy used in plyometric training. For example, if you drop down into a squat before you perform a vertical jump, you will jump higher than if you started with just a slight bend of the knees. Rapidly dropping into a squat forcefully extends the quadriceps muscles. The body activates the stretch reflex and contracts the muscle. If you jump at this moment, you can use the force of the stretch reflex contraction to propel yourself into the air.
Pullups
Transferring this idea to the biceps muscles allows you to power yourself during the pullup exercise. Grab onto a pullup bar and suspend yourself with your chin at or above the bar. Rapidly drop your body down until your arms are fully extended. This will trigger the body's stretch reflex in the biceps muscles. Use the sudden contraction of the biceps muscles to assist yourself in pulling your body back up to the bar. Although you need to descend quickly to activate the stretch reflex, ensure that you descend with control or you could hyperextend your elbow or strain your biceps muscles.
References
- University of Nebraska Medical Center; The Nervous System In Action: Reflexes; Michael D. Mann; July 21, 2008
- "NSCA Journal"; Plyometrics--More Than the Stretch Reflex; David W. Thomas, et al.; 1988
- "NSCA's Performance Training Journal"; Practical Progressions for Upper Body Plyometric Training; Mark Nutting
- University of California San Diego; A Practical Guide to Clinical Medicine; Charlie Goldberg
